Hypertension is the most common cardiovascular disease and is also a major risk factor leading to increased morbidity and mortality of congestive heart failure, stroke, coronary heart disease, renal failure, and aortic aneurysms. Antihypertensive drugs play an important role in the treatment and prevention of hypertension. With the deepening of the understanding of the pathogenesis of hypertension, many antihypertensive drugs with better curative effects, such as diuretics, β-blockers, calcium channel antagonists, angiotensin converting enzyme inhibitors (ACEI,-pril), Angiotensin II AT1 receptor antagonist (ARB, sartan), has been continuously discovered and successfully applied in clinical practice. After years of clinical practice, it has been confirmed that the sartan of the AT1 receptor antagonist, due to its stable antihypertensive effect, good curative effect, long duration of action, good patient tolerance as well as many advantages especially in preventing stroke, delaying diabetes and non-diabetic nephropathy, improving left ventricular hypertrophy and protecting target organs, without affecting bradykinin degradation and prostaglandin synthesis so as not to cause dry cough and angioedema, has become the mainstream of the global antihypertensive drug market. However, the effective ratio of sartan antihypertensive drugs is only about 50-60%, and there exists a certain degree of adverse effect of sartans. Therefore, the development of a small-dose as well as long-acting antihypertensive drug with stronger antihypertensive effect, less adverse effect and better protection of target organs has become a hot research direction.
The Chinese Patent Application (Publication No. CN103709154A) discloses a compound of the formula (B) for the first time:

The above compound is a sartan drug which is coupled with ligustrazine and is a prodrug of angiotensin II receptor antagonist azisartan (TAK-536). The compound releases hydroxyprosin in vivo, which makes an effective synergistic action with azilsartan, accordingly enhancing its antihypertensive effect as well as contributing to reduction of heart rate and adverse effect, and further bringing desired protective effect on the heart and kidney of patients.
A potassium salt of compound (B), represented by the compound of formula (A) as below, has been discovered by the applicant in further studies, which has better solubility, higher bioavailability, more potent and longer-lasting antihypertensive effect, more obvious and sustainable effect of lowering heart rate, higher safety, as well as desired protective effect on the heart and kidney function of patients, and can be used for preventing and/or treating hypertension, chronic heart failure, diabetic nephropathy, and the like,

However, there is still demand for further development of a more suitable form of the above compounds.